Beautiful binocular clusters

I’m chasing Messier objects with binoculars at the moment. To be honest most aren’t all that impressive, but whilst searching out these objects in Ophiuchus I encountered something fabulous.

I found a huge cluster of bright stars with an obvious profusion of faint stars forming the background field. It immediately struck me that after a lean time on Messiers this object was what binoculars were made for.

But I wasn’t done!

As usual I let the field wander around only to catch sight of an even more impressive cluster. This one wasn’t as big, that much was immediately evident, but it sported a bright band of stars from north to south through the middle of a rich cluster.

A quick look at my copy of Sky & Telescope’s Pocket Sky Atlas told me that what I had originally found was the open cluster IC 4756, and that I was now gazing upon the splendour of NGC 6633. Here’s an idea of what they look like provided by Carte du Ciel, but it’s nothing like the real thing.

The red circle around NGC 6633 shows a 4 degree field of view which is pretty modest for moderate power binoculars. My 15×70 binoculars have about this field, and my 10x50s give about 5 degrees. So you can see why these are such good binocular objects. First they’re a bright starry magnitude 4 to 5, and secondly they’re really big, I would guess at least a degree across.

They’re not particularly hard to find either. There are plenty of bright stars around to help and binoculars are great for star hopping. Here’s a sky map courtesy of Stellarium to help.

You’re missing out if you haven’t seen these two, so if you’ve got a pair of binocular take a look before they disappear into the morning glare until next year.